To avoid engine-killing sludge buildup, you must pick the right oil-change schedule, either normal or severe. This will involve an honest evaluation of your driving habits. Highway driving is easy on cars. Short trips and traffic are extremely hard on cars. Whichever you do more often determines how many miles or months you can go between changes. It's your decision, but be realistic. If there's doubt, use the severe service schedule.
If your manual reads like most, you'll see that many manufacturers are recommending oil change intervals that are higher than they were in the past. Some recommend oil changes every 5,000, 7,500, or even every 10,000 miles. Sticking to these schedules is great-if your oil is up to the task.
Fortunately, motor oil manufacturers are responding to this trend. ExxonMobil recently became the first major oil company to introduce a "high endurance" line of oils. The line includes three products-Mobil Clean 5000, Mobil Clean 7500 and Mobil 1 Extended Performance-which provide guaranteed protection for 5,000, 7,500, and 15,000 miles, respectively. If you're going to stick to the schedules your manufacturer recommends, make sure your oil is up to the task. Even if you decide to go less than 5,000 miles between changes, make sure you use high quality oils like the Mobil offerings.
Second to changing engine oil is properly maintaining your cooling system. To be safe, check the coolant, and all vehicle fluids, according to the shortest time or distance recommended, not the longest. Coolant, even extended-life variants, should be tested for condition every six months and coolant levels should be checked monthly. Proper testing may prompt you to flush and refill long before the extended-life interval has been achieved. A word of warning: never allow coolant to stay in the radiator until it changes color, because that change indicates rust, and rust is essentially dissolved engine.
Last, but not least, is the automatic transmission, which can usually live long and deliver good service if given a little help. Help means flushing the transmission and renewing its fluid every two years or 24,000 miles. Unlike old-fashioned transmission service, where only about a third of the fluid was changed, flushing changes all the fluid. Chemicals are also used in the flush process to dissolve harmful deposits and dramatically extend transmission life.
Never cheat on maintenance. Maintenance cheaters rationalize and justify poor maintenance decisions with highly imaginative theories, but they ultimately only cheat themselves. You can't fool metal. Metal doesn't have feelings. It's impossible for metal parts to disregard forgotten or cheap penny-pinching, dollar-foolish, inadequate maintenance! Improper maintenance means prematurely worn parts and high repair bills. Proper maintenance provides reliability, longevity and, peace of mind.